Introduction
C# developers who are interested in console programming are often frustrated by
the lack of user interface features which the console has compared to Windows
Forms and WPF applications.
Well, despite the limitations of its text based interface, you can with a bit of
effort produce console versions of some of the simpler windows 'controls' and in
this article I'd like to show you how to produce a listbox.
To do this we need to draw a box on the console and, fortunately, the unicode
character set (as did MS-DOS code pages before it) supports a number of box
drawing characters (see
http://en.wikipedia.org/wiki/Box-drawing_characters).
Source Code
Here's the source code for producing a basic listbox containing the names of the
12 months of the year:
using
System;
class ConsoleListBox
{
static void
Main()
{
Console.TreatControlCAsInput =
false;
Console.CancelKeyPress +=
new
ConsoleCancelEventHandler(BreakHandler);
Console.Clear();
Console.CursorVisible =
false;
string[] months = {"January",
"February",
"March", "April",
"May", "June",
"July", "August",
"September",
"October", "November", "December"};
WriteColorString("Choose Level using down and up
arrow keys and press enter", 12, 20,
ConsoleColor.Black, ConsoleColor.White);
int choice = ChooseListBoxItem(months, 34, 3,
ConsoleColor.Blue,
ConsoleColor.White);
// do something with choice
WriteColorString("You chose "
+ months[choice - 1] + ". Press any key to exit",
21, 22, ConsoleColor.Black,
ConsoleColor.White);
Console.ReadKey();
CleanUp();
}
public static int ChooseListBoxItem(string[]
items, int ucol, int
urow, ConsoleColor back,
ConsoleColor fore)
{
int numItems = items.Length;
int maxLength = items[0].Length;
for (int
i = 1; i < numItems; i++)
{
if (items[i].Length > maxLength)
{
maxLength = items[i].Length;
}
}
int[] rightSpaces =
new int[numItems];
for (int
i = 0; i < numItems; i++)
{
rightSpaces[i] = maxLength - items[i].Length + 1;
}
int lcol = ucol + maxLength + 3;
int lrow = urow + numItems + 1;
DrawBox(ucol, urow, lcol, lrow, back, fore,
true);
WriteColorString(" " + items[0] +
new string(' ', rightSpaces[0]), ucol + 1, urow + 1, fore, back);
for (int
i = 2; i <= numItems; i++)
{
WriteColorString(items[i - 1], ucol + 2, urow + i, back, fore);
}
ConsoleKeyInfo cki;
char key;
int choice = 1;
while (true)
{
cki = Console.ReadKey(true);
key = cki.KeyChar;
if (key ==
'\r') // enter
{
return choice;
}
else if
(cki.Key == ConsoleKey.DownArrow)
{
WriteColorString(" " +
items[choice - 1] + new
string(' ', rightSpaces[choice - 1]),
ucol + 1, urow + choice, back, fore);
if (choice < numItems)
{
choice++;
}
else
{
choice = 1;
}
WriteColorString(" " +
items[choice - 1] + new
string(' ', rightSpaces[choice - 1]),
ucol + 1, urow + choice, fore, back);
}
else if
(cki.Key == ConsoleKey.UpArrow)
{
WriteColorString(" " +
items[choice - 1] + new
string(' ', rightSpaces[choice - 1]),
ucol + 1, urow + choice, back, fore);
if (choice > 1)
{
choice--;
}
else
{
choice = numItems;
}
WriteColorString(" " +
items[choice - 1] + new
string(' ', rightSpaces[choice - 1]),
ucol + 1, urow + choice, fore, back);
}
}
}
public static void DrawBox(int
ucol, int urow, int
lcol, int lrow,
ConsoleColor back, ConsoleColor fore,
bool fill)
{
const char
Horizontal = '\u2500';
const char
Vertical = '\u2502';
const char
UpperLeftCorner = '\u250c';
const char
UpperRightCorner = '\u2510';
const char
LowerLeftCorner = '\u2514';
const char
LowerRightCorner = '\u2518';
string fillLine = fill ?
new string('
', lcol - ucol - 1) : "";
SetColors(back, fore);
// draw top edge
Console.SetCursorPosition(ucol,
urow);
Console.Write(UpperLeftCorner);
for (int
i = ucol + 1; i < lcol; i++)
{
Console.Write(Horizontal);
}
Console.Write(UpperRightCorner);
// draw sides
for (int
i = urow + 1; i < lrow; i++)
{
Console.SetCursorPosition(ucol, i);
Console.Write(Vertical);
if (fill)
Console.Write(fillLine);
Console.SetCursorPosition(lcol, i);
Console.Write(Vertical);
}
// draw bottom edge
Console.SetCursorPosition(ucol,
lrow);
Console.Write(LowerLeftCorner);
for (int
i = ucol + 1; i < lcol; i++)
{
Console.Write(Horizontal);
}
Console.Write(LowerRightCorner);
}
public static void WriteColorString(string
s, int col, int
row, ConsoleColor back,
ConsoleColor fore)
{
SetColors(back, fore);
// write string
Console.SetCursorPosition(col,
row);
Console.Write(s);
}
public static void SetColors(ConsoleColor
back, ConsoleColor fore)
{
Console.BackgroundColor = back;
Console.ForegroundColor = fore;
}
public static void CleanUp()
{
Console.ResetColor();
Console.CursorVisible =
true;
Console.Clear();
}
private static void BreakHandler(object
sender, ConsoleCancelEventArgs args)
{
// exit gracefully if Control-C or
Control-Break pressed
CleanUp();
}
}
Output
When you build and run this program, the console should look like this :
